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During the opening credits of the hip new comedy “Juno,” a tune written and performed by Silver Spring’s own Barry Louis Polisar plays in the background. The sweet acoustic love song is titled “All I Want Is You,” and it drips with honeyed metaphors like: “If you were the winter, I know I’d be the snow/ As long as you were with me, let the cold wind blow.”

The guitar-and-harmonica ballad provides an apt point-of-entry into “Juno’s” PG-13 tale of complicated teen relationships; however, as a representation of Mr. Polisar’s body of work, the song may be a bit misleading. For the past 30-some years, the artist has been creating music and books for G and PG crowds — in other words, children.

If this information comes as a surprise to “Juno” watchers, that’s a coincidence — because Mr. Polisar himself was surprised that he ended up becoming a children’s entertainer.

In elementary school, he owned a guitar and was a Johnny Cash fan, but he never really thought about pursuing music professionally. When he entered college in the 1970s, he did so with hopes of becoming a teacher.

While he later ended up changing his course of studies to film and literature, the college-aged Mr. Polisar did receive an invitation to perform music at a school, where two fortuitous things happened: The crowd loved him, and he got the real-life inspiration to write a ditty called “I’ve Got a Teacher, She’s So Mean.” With that silly song, written from a child’s perspective, something clicked for Mr. Polisar. Up to this point he’d been penning tunes in several different styles, but he hadn’t yet found a musical voice of his own.

“All the genres I wrote in sounded like other people’s songs to me,” the artist says, speaking by phone from his Silver Spring home. “Nothing sounded fresh and original, and when I wrote my first children’s song I thought, ‘Wow, this is really different.’ ” He recorded his first children’s album, “I Eat Kids and Other Songs for Rebellious Children,” in 1975 while still in college. “It didn’t cost much,” Mr. Polisar says. “I did it in one take with one mike. It was a pretty rudimentary album, but lo and behold, I sold out of all 1,000 copies.”

Mr. Polisar says that at this early stage, he saw music-making not as a job but as a fun “art project.” When demand for his albums and live performances continued post-graduation, however, he found himself changing his tune.

The pioneering children’s entertainer currently has a resume that would make many in his niche nervous. He’s produced more than a dozen albums and nearly as many children’s books, done live programs in most of the 50 states and D.C. (including at the White House and Kennedy Center), toured Europe several times and starred on an Emmy-winning children’s show, “Field Trip.”

Generations of youngsters and even “Sesame Street’s” Big Bird have sung Mr. Polisar’s colorful tunes. Among his most popular ditties are “Don’t Put Your Finger Up Your Nose” and “I’m a 3-Toed, Triple-Eyed, Double-Jointed Dinosaur” (both of which are familiar reminders of this reporter’s past).

Despite these successes (and a headline-making censorship battle with Anne Arundel County schools in the ‘90s), the artist has kept a fairly low profile over the years. He’s operated independently, relying on word-of-mouth and his Web site (www.barrylou.com) for promotion. This has allowed him to retain creative control over his work, to have a flexible schedule that includes family time (he is married and has two children), and to stay accessible to fans and potential clients. Until recently, Mr. Polisar even had his home address posted online.

It remains to be seen how the inclusion of “All I Want Is You” on the “Juno” soundtrack will change his life and career dynamics. (The record is currently No. 1 on ITunes’ album chart.) Yet, the musician says that director Jason Reitman’s chance discovery of and decision to use the song has already had a huge emotional impact on him.

“I’m getting e-mails daily from people who [saw ‘Juno’ and] had my albums as kids,” Mr. Polisar says. “One said yesterday that she just about screamed when she heard the first bar of the song come on; she recognized it immediately.” He later adds, “There have been blips in my career where big stuff has happened, but this is probably bigger than anything else. This is validation somehow.”

Until Hollywood comes knocking again, Mr. Polisar will continue with his usual slate of school and library performances. On Monday, he’ll be at Lisbon Elementary School in Woodbine, Md., and on Wednesday, Sunderland Elementary School in Sunderland, Md. For information on upcoming public performances, stay tuned to the artist’s Web site.